After an absence from academic research, I chose to return to the University of Florida to be a part of its internationally recognized Diabetes Research Group. As a junior member of this distinguished group, I have access to human and animal samples for parallel studies of the immunopathogenesis of Type 1 diabetes, and the support a large, diverse university's resources for advanced technology, collaboration, and funding. I have a wide breath of technical skills, especially in the design or adapt methodology. However, my further development as a research scientist depends on refining these skills to execute a focused research plan. The writing of this KO1 Career Development Award proposal gives me the opportunity to gain experience in crucial areas where I lack depth: clinical research design, grant project development, and scientific authorship. This proposal addresses fundamental defects in antigen presenting cell (APC) function important in immunopathogenesis of Type 1 Diabetes (IDDM). We have reported a biochemical component of APC dysfunction in diabetic/at-risk humans and in the Nonobese diabetic (NOD) mouse: the aberrant expression of the normally inducible cyclooxygenase, prostaglandin synthase 2 (PGS2/COX2). Sequence analysis indicates this phenotype is not due to a cis defect in the PGS2 structural gene or its immediate 5' or 3' regions. These finding suggest that components further up- or downstream and/or trans acting molecules may be responsible for its aberrant expression. In our analysis of trans acting factors, we found that PGS2 expression in NOD macrophages and in the peripheral blood monocytes of 55% of at- risk/IDDM subjects tested was resistant to IL10 suppression. In addition, the PGS2 expression of these cells could be further enhanced by even a brief exposure to GM-CSF(granulocyte monocyte colony stimulating factor). In contrast, PGS2 expression of control cells is not induced by treatment with GM-CSF and is IL 10 sensitive after LPS (lipopolysaccharide) induction. These aspects of NOD/IDDM PGS2 expression are not due to a defect in IL 10 production or its general functional activity, but appears to be linked to GM-CSF activation of STAT5, a transcription regulator of the PGS2 gene's enhancer. Preliminary analyses indicate a loss of DNA binding of STAT dominant negative repressor (truncated) isoforms and a persistence of binding of its full-length activator forms may contribute to aberrant PGS2 expression seen in NOD and at-risk/IDDM human myeloid cells. Our goal is to examine STAT5 signal transduction/transcription regulation in Type 1 diabetic patients, their at-risk relatives, and in the NOD mouse, and determine its 1) role in monocyte and macrophage PGS2 expression dysregulation, 2) possible effects on myeloid differentiation, and 3) relationship to APC dysfunction in the immunopathogenesis of Type 1 Diabetes.